A superconducting coil formed by winding a superconducting wire has been disclosed (for example, Japanese Examined Patent Application Publication No. 7-79048 (Patent Literature (PTL) 1)). PTL 1 discloses a method of connecting saddle-shaped superconducting magnet coils. PTL1 discloses connection of the saddle-shaped superconducting magnet coils by superposing an inner layer coil and an outer layer coil on each other, the inner and outer layer coils being formed by winding superconducting wires having sectional dimensions different from each other, and connecting the inner and the outer layer coils in series.